1. Field of the Invention
This invention relates to wind turbines, and in particular wind turbines having a vertical axis and a variable number of stackable blades.
2. Brief Description of the Prior Art
Alternative energy sources are greatly needed as the world reaches peak oil. Coal is still plentiful, and would last possibly for centuries, but the pollution and environmental destruction caused by the coal industry is unsustainable. Wind energy is one great source of renewable energy. The majority of wind energy is produced with extremely large horizontal axis turbines. One of the problems with these turbines is the turbulence created by these large blades. As a result of this turbulence, these turbines must be spaced three to ten times their diameter apart (side to side) and in rows five to ten times their diameter apart, which, for a 300 foot diameter turbine, would be up to 3,000 feet apart (side to side) and the rows of turbines up to 3,000 feet apart as well. This creates a very inefficient use of the available land.
Many patents have been issued to inventions related vertical axis turbines but none of these inventions are disclosing the use of two counter-rotating turbines incased into two cambers at the sides of an aero-dynamical foil shaped as two joined airplane wings. The foil also functions as a rudder to position the system against the direction of the blowing wind.
This positioning of the turbines inside this specially-shaped foil generates much less turbulence than all other reference turbines, greatly increasing potential output and allowing the electric generators to be more closely spaced. The widespread use of the shrouded vertical axis dual-turbine Generator as disclosed will greatly increase the amount of energy produced from wind. The Shrouded vertical axis dual-turbine generator can also be used submerged in water as a high output source of energy, having a low profile, without negatively affect tourist coastal areas.
U.S. Pat. No. 5,580,108 of inventor Bernard discloses a dual turbine system that attempts to takes advantage of the Bernoulli's principle, to increase energy output by splitting the flow around a leading edge to power turbines on each side. Bernard sought to increase output with the use of a foil, adjusting the flow of air over the turbines by moving the turbines in and out the flow to expose them to more or less flow, thus adjusting their speed.
U.S. Pat. No. 6,942,454 of inventor Ohlmann discloses a dual turbine system that splits the flow around a leading edge to the turbines on each side, and regulates the amount of flow using two movable deflector flaps. In the present invention, instead, the speed of the turbines is regulated by opening and closing two shutters on the sides of the foil.